Gas Sensor Readout Using Asynchronous Counting for Drift Accuracy
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Solution Overview
Problem
Gas sensors face challenges in accurately measuring resistance changes due to temperature drift and inaccuracies in process parameters, particularly in resistive gas sensors, which affect the reliability and accuracy of air quality monitoring and other sensor applications.
Innovation Solution
A gas sensor arrangement and method that employs a measurement frontend with a first-order modulator or continuous time integrator, using asynchronous counters and fractional time counts to correct for errors and account for temperature drift, allowing for ratiometric calculations and detection of sensor disconnection, while maintaining low power and area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a measurement frontend is used to evaluate sensor output, then the sensor can detect resistance changes, but temperature drift and process parameter inaccuracies reduce measurement accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the measurement frontend continuously monitors the sensor output and adjusts its evaluation based on detected temperature drift and process parameter variations. This closed-loop approach compensates for environmental influences and maintains measurement accuracy across varying conditions.
Solution Approach 2:
The system dynamically adjusts measurement parameters such as integration time, excitation current, and threshold voltages based on detected temperature and resistance ranges. This adaptive parameter adjustment optimizes measurement precision across the wide dynamic range from 1 kΩ to 1 GΩ while compensating for temperature drift effects.
2Adaptability or versatility
If the measurement range is extended to cover low and high resistances, then the sensor can monitor diverse gas concentrations, but errors from first-count and residue count increase
Solution Approach 1:
The patent applies preliminary correction actions by calculating and compensating for first-count errors and residue count errors before final measurement evaluation. The system pre-characterizes these errors across the measurement range and applies compensatory algorithms to maintain accuracy at both low and high resistance extremes.
Solution Approach 2:
The patent replaces traditional mechanical counting methods with a digital signal processing approach that uses asynchronous counters and fractional time counts. This substitution enables error correction through mathematical operations rather than mechanical counting, significantly improving precision across the extended dynamic range.
3Measurement precision
If integration time is extended to improve measurement accuracy, then resistance measurements become more precise, but the response time and productivity decrease
Solution Approach 1:
The patent implements dynamic integration time adjustment where the system automatically selects optimal integration durations based on the measured resistance range and environmental conditions. For stable readings in moderate ranges, shorter integration times maintain high throughput, while extended integration is applied only when higher precision is required or conditions are unstable.
Solution Approach 2:
The measurement system employs periodic sampling with variable integration times rather than continuous long-duration measurements. This periodic approach with adaptive timing maintains measurement precision while enabling frequent updates and high productivity through efficient use of measurement cycles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides accurate resistance measurements across a wide dynamic range (1 kΩ to 1 GΩ) with reduced error, enabling reliable gas sensing and detection of sensor disconnection, while minimizing the impact of temperature drift and process parameter inaccuracies.
Implementation Method 1
In resistive gas sensors a semiconductor material is exposed to a gas such that the electrical resistance in the sensor is decreased or increased when it comes in contact with the monitored gas
Data Source
AI summary
In an embodiment a method for operating a gas sensor arrangement includes generating a sensor current by a gas sensor, converting the sensor current into a digital comparator output signal in a charge balancing operation depending on a first clock signal, determining from the digital comparator output signal an asynchronous count comprising an integer number of counts depending on the first clock signal, determining from the digital comparator output signal a fractional time count depending on a second clock signal and calculating from the asynchronous count and from the fractional time count a digital output signal which is indicative of the sensor current generated by the gas sensor.